Abstract

Mineral dust aerosols play an important role in climate and the Earth's energy
budget. The effect of dust on the radiative forcing is uncertain due to the complexity of
particle properties and the complexity to quantify and discriminate preferential dust
sources. This research considers the potential of two Regional Climate Models (RCM’s):
The Weather Research and Forecasting model (WRF-Chem) and the Regional Climate
Model (RegCM3) both with an integrated dust module. Numerical sensitivity experiments
are performed to quantify the ability of both models to simulate sources, the magnitude of
dust emission, the transport in 3-dimensions and the subsequent impact on the radiative
forcing. Particular emphasis is given to preferential source regions within the Sahara and
Sahel in North Africa including the Bodélé Depression in Northern Chad. To account for
the distribution of preferential dust source regions, soil texture characteristics were
modified in dust source regions in RegCM3. As for WRF-Chem GOCART scheme, a new
higher resolution erodible fraction map is tested. Moreover, the sensitivity of the results to
the specification of aerosol optical properties to evaluate the impacts of optical
characteristics on the radiative forcing was considered for the RegCM3. Finally, model
outputs are compared to in-situ data: weather stations (WMO) and AERONET and
satellite estimates: MODIS, MISR, OMI, CALIPSO and SEVIRI. Results show that both
models represent the space/time structure of near-surface meteorology well. The tuning of
preferential dust sources tested in this research provides a more realistic representation of
local dust sources, emissions and resulting AOT. This suggest that in the absence of truly
accurate soil maps at high resolution, further refinements to preferential sources map and
its implementation in dust models can lead to useful improvements in simulation of dust
processes and dust forecast accuracy.

Type:

Thesis
(Doctoral)

Title:

Modelling the atmospheric controls and climate impact
of mineral dust in the Sahara Desert